Conference phones are commonly used in a number of environments, such as meeting rooms, conference rooms, boardrooms and the like, to allow a group of people at a single location to participate in a phone call.
Many standard telephone sets can provide rudimentary conference abilities through a handsfree mode that uses a speaker and a microphone to communicate audio larger distances from the handset. To avoid echo, many such telephone sets employ half duplex switching so that the microphone and speaker are not active simultaneously. While half duplex switching allows a number of people to sit at a single location and participate in a call, there are a number of short comings to such a rudimentary conferencing capability. For instance, any noises in the room will cut off the far-end audio. Thus speaking, coughing, or paper shuffling will all prevent any inbound audio from being heard. This soon results in halting discussion patterns over the telephone link to the point where even a request to repeat a missing point may not be heard.
A conference phone is typically defined by having two features. The first feature is the ability to provide a speaker supporting full duplex audio capability that permits simultaneous transmission and reception of audio, and the second feature is a multi-line capability which provides the ability to use more than one phone line to serve as a rudimentary conference bridge. The availability of third party dial in conference bridges has made the multi-line capability feature of these phones redundant to a certain degree, but the feature is still considered to be a standard conference phone offering.
In large environments, a simple telephone handset in a speakerphone mode is unsuitable as a conference room phone. In large rooms, the audio quality provided by standard speakerphone implementations is not sufficient. To address this problem, dedicated conference phones are provided.
Dedicated conference phones, such as those offered by Polycom, Inc., ClearOne etc. provide only a handsfree experience. The conventional handsfree conference phone provides a dial pad and display to allow the user to dial and create a conference session. The phone typically has a plurality of microphones, and a single speaker. By using a plurality of microphones, the system can switch between active and passive microphones based on the position of a person speaking.
One common problem with conference phones is echo. When a remote participant in the call speaks, the voice is reproduced through the speaker of the unit. This sound is then received by the microphones as input, and is provided back to the remote participant with a slight delay. This causes an apparent echo that is often found to be distracting. To address this matter early solutions employed a half-duplex design, so that the microphones and the speaker do not operate simultaneously. A more sophisticated full duplex solution is presently found in dedicated conference phones. The full duplex solution makes use of echo-canceling circuitry to analyze the received signal and subtract that signal from the signal generated by the microphones allowing the speaker and microphones to operate simultaneously.
To address the needs of larger boardrooms, many conference phone systems make use of slaved microphone units that allow corded satellite units to connect to a central unit. The echo cancellation then factors in the sounds received at all the microphones, including those from the satellite units.
Recently wireless conference phones have been introduced to allow the phone to be moved between conference rooms or to be easily repositioned in a conference room. These wireless units are virtually identical to their wired analogs, but replace the cord between the phone and a wall jack with a wireless link to a base station connected to the telephone wall jack. These wireless units do not typically offer satellites, and when they do, the satellites are connected to the phone with wires, thus limiting the high degree of mobility and flexibility offered by the wireless phone unit. These wireless units cannot serve large meeting rooms without the ability to attach satellite units.
Outside of conference phones, simply using a plurality of telephone handsets connected to a single base station is known. This has not been implemented for conference phones due to the great complexity of dealing with echo cancellation across a plurality of different phones each connected to the base station but not to each other.
It is, therefore, desirable to provide a wireless conference phone system with the ability to support larger conference rooms.